A spark plug is attached to, for example, an internal combustion engine (engine), and is used for igniting an air-fuel mixture within a combustion chamber. In general, such a spark plug includes a tubular insulator extending in the direction of an axis; a center electrode inserted into the insulator; a metallic shell provided around the insulator; and a ground electrode provided at a forward end portion of the metallic shell and forming a spark discharge gap in cooperation with the center electrode. The metallic shell and the insulator are fixed together by inserting the insulator into the metallic shell and applying a load along the direction of the axis to a rear end opening portion of the metallic shell through use of a predetermined die to thereby bend the rear end opening portion inward in the radial direction (i.e., through a crimping step).
Further, there has been known a technique of disposing talc between the metallic shell and the insulator in order to enhance the airtightness between the metallic shell and the insulator (see, for example, Japanese Patent Application Laid-Open (kokai) No. 2006-92955 “Patent Document 1”).